VSCode Load File in REPL error: readline-input:1:0: #%top-interaction: unbound identifier

[gussmith23]

When I use the Load File in REPL command on an otherwise empty Racket file:

#lang errortrace racket

It runs the following command:

racket --repl --eval '(enter! (file "/Users/gus/tmp0.rkt"))'

The REPL loads, but when I run any command in the REPL I get the following error:

"racket/tmp0.rkt"> 1
; readline-input:1:0: #%top-interaction: unbound identifier;
;  also, no #%app syntax transformer is bound
;   at: #%top-interaction
;   in: (#%top-interaction . 1)
; [,bt for context]

Can this be fixed?

[sorawee]

#lang errortrace does not support REPL. It probably should. But meanwhile, I would avoid #lang errortrace and invoke errortrace as described in the documentation.

$ cat test.rkt
#lang racket

(define (fact n)
  (cond
    [(zero? n) (/ 1 0)]
    [else (* n (fact (sub1 n)))]))

(fact 3)
$ racket --repl -l errortrace -e '(enter! (file "/Users/soraweep/test.rkt"))'
Welcome to Racket v8.5.0.8 [cs].
/: division by zero
  errortrace...:
   /Users/soraweep/test.rkt:5:15: (/ 1 0)
   /Users/soraweep/test.rkt:6:10: (* n (fact (sub1 n)))
   /Users/soraweep/test.rkt:6:10: (* n (fact (sub1 n)))
   /Users/soraweep/test.rkt:6:10: (* n (fact (sub1 n)))
...
"~/test.rkt"> (fact 2) ;; REPL is usable
/: division by zero [,bt for context]
"~/test.rkt"> ,bt
/: division by zero
  errortrace...:
   /Users/soraweep/test.rkt:5:15: (/ 1 0)
   /Users/soraweep/test.rkt:6:10: (* n (fact (sub1 n)))
   /Users/soraweep/test.rkt:6:10: (* n (fact (sub1 n)))
...

[sorawee]

Without #34, the behaviors of Racket CS and Racket BC are also different.

Steps to reproduce:

1. Install snapshot versions of Racket BC and Racket CS.

2. Create a file /path/to/file.rkt with the following content:

   #lang errortrace racket
   (define x 1)
   

3. Run /Applications/Racket\ v8.6.0.2\ CS/bin/racket --repl --eval '(enter! (file "/path/to/file.rkt"))'. Evaluating 1 results in string:1:0: #%top-interaction: unbound identifier;.

4. Run /Applications/Racket\ v8.6.0.2\ BC/bin/racket --repl --eval '(enter! (file "/path/to/file.rkt"))'. Evaluating 1 results in 1. Evaluating x results in x: undefined; cannot reference an identifier before its definition.

I believe Racket CS is more correct here, since #lang errortrace does not provide #%top-interaction.

[sorawee]

This probably should be reopened, since the fix above is not the right one, and got reverted.

[mflatt]

I think the issue is that #lang errortrace ends up expanding the module body in a way that gives it extra scopes, and those scopes are not the ones that module->namespace will set up for namespace-syntax-introduce.

Maybe something like the code below would be a good direction in errortrace/lang/body.rkt. It binds #%top-interaction to a macro that adds the extra scopes.

(define-syntax (module-begin stx)
  (syntax-case stx ()
    [(_ orig-lang . body)
     (let ([e (errortrace-annotate #`(module . #,(strip-context #`(n orig-lang . body))))])
       (syntax-case e ()
         [(mod nm lang (mb . body)) 
          #`(#%plain-module-begin 
             (require (only-in lang)
                      (only-in errortrace)) ; to set the display handler
             (define-syntax (#,(datum->syntax #'orig-lang '#%top-interaction) stx)
               (define delta (make-syntax-delta-introducer #'lang #'orig-lang))
               (syntax-case stx ()
                 [(_ . e)
                  #`(#%top-interaction . #,(delta #'e))]))
             . body)]))]))

[mflatt]

Another possibility would be to change the macro expander to allow a #%module-begin macro to control the scopes that are used for namespace-syntax-introduce. That could take the form of a new #%declare option. Currently, #%declare offers limited control in the form of #:empty-namespace, which roughly does something like setting the relevant scope set to empty.